Our goal is to study the various factors that affect oxygenation of the fetus-in-utero. We will determine the precise relation of fetal and maternal blood carbon dioxide tensions to osmotic pressures, and in turn to the placental transfer of water. We will also study the interrelations of fetal water volume, blood volume, venous return and cardiac output. We are also studying the role of several factors in regulating venous return including: mean systemic pressure, venous vascular compliance and the resistance to return. We will also determine the possible role of cytochrome P-450 in facilitating oxygen diffusion in the placenta and fetal tissues. We are also using mathematical modeling to understand the role of various factors affecting oxygen delivery to fetal tissues.